1. Field of the Invention
The present invention relates to apparatus for fabricating trusses and other frame structures composed of wooden frame members and more particularly to a jig table for assembling the frame members, a press for pressing metal connector plates into the butt joints of the assembled frame members, and associated components of each.
2. Description of the Prior Art
Prior systems for fabricating wooden trusses take various forms. However, in all forms there is some sort of means for supporting the wooden frame members to be joined during assembly and fastening, usually either a large jig table which supports the entire truss or a series of small support stands, each of which supports only one or a few of the several butt joints of the truss members. Means are also provided for pressing a pair of connector plates into the wooden frame members at each butt joint. The latter means usually takes the form of a hydraulically actuated press, usually of the reciprocating type. However, there are also roller presses wherein an assembled truss supported on a movable table or platen is moved between a pair of rollers which squeeze the connector plates into the joint as the truss moves through the rollers.
There are basically two types of truss-fabricating systems. One type is exemplified by U.S. Pat. No. 3,443,513 in which a movable table supporting the assembled wooden frame members moves through a stationary press. The other type is exemplified by U.S. Pat. No. 3,603,244 in which a movable press moves along a stationary jig table supporting the truss members to be assembled. A major advantage of the stationary table-movable press system over the other system is that the former requires substantially no more space than needed to support the largest truss to be manufactured while the latter requires a work area at least twice the length of the longest truss made. Another substantial advantage of the movable press-stationary table system over the other system is that in the former the truss members themselves need not be moved, enabling the fabrication of a more accurate, tighter fitting, and thus stronger truss than is usually possible with the stationary press-movable table system.
The stationary table-movable press system is relatively new, primarily because of the problem of moving a press along a table without conflict with the table legs. Most of such systems take the form shown in U.S. Pat. No. 3,603,244 in which a closed-throated press spans the jig table and moves along tracks at opposite sides of the table. The table itself is supported on a complex system of special pivotable, so-called "grasshopper" legs which must swing from one position to another to permit the lower portion of the press to pass slowly beneath the jig table. In this system, press forces are transmitted between upper and lower press platens through the jig table, so the table must be of sufficient strength and thickness to withstand these high forces.
Another type of fixed stand-movable press system is shown in U.S. Pat. No. 3,068,484 in which individual stands shiftable along tracks support the individual butt joints of the truss frame members and a small press movable along an overhead track is moved from stand to stand manually to embed connector plates at each joint. Each stand is shifted to a new position to correspond to the changed positions of a truss joint each time a different type or size of truss is to be produced.
Still another type of truss-manufacturing system is exemplified by U.S. Pat. Nos. 3,530,790 and 3,460,465 in which separate track-mounted truss support stands and integral presses are provided at each separate truss joint to support the truss and embed the connector plates. This type of system also requires shifting of each separate press-stand under the last-described circumstances.